1. Technical Field
The present invention relates in general to spray dispensers for applying liquids and, in particular, to an improved system, method, and apparatus for an agitated and pressurized reservoir that is mounted directly to a paint spray dispenser.
2. Description of the Related Art
In laboratory research and development, very small quantities of experimental radar absorbing materials (RAM) are carefully applied to test articles in a paint-like form using automated spray dispensing systems. Because of the extremely limited availability and extraordinary cost of some experimental RAMs (i.e., some on the order of $40,000 per gallon), only very small volumes on the order of one pint or less are available for research and development.
During the spray application process, RAM require constant agitation to prevent the critical filler components from settling in the suspending liquid in order to provide a highly homogenous application with very consistent physical properties. Non-agitation results in irregular material feed rates and inconsistent applications that compromise system performance. Accurate and repeatable spray application of small quantities of RAM currently presents a significant problem.
Although there are several types of spray systems that meet some of the requirements for applying RAM, there is no existing commercial spray system that meets all of the requirements for applying experimental quantities of RAM. Existing spray systems that are compatible with limited volume materials use one of two general classes of automated paint delivery and application systems. The first type is a suction or gravity-fed system with a small volume (e.g., one quart) paint reservoir or “pot” mounted on the dispenser or “gun.” With suction devices the pot is typically located below the gun, while with gravity-fed devices the pot is located above the gun. The second type of system comprises a pressurized, large volume pot (e.g., 5 gallons) that is separated and located upstream from the gun. A hose having a length of about 10 to 50 feet is used to deliver the paint from the pot to the gun.
These existing spray systems have several limitations that make their use difficult for experimental RAM application. For example, current suction or gravity-fed RAM application systems do not contain an agitation mechanism, such as the propellers rotated at the bottoms of large volume pots to provide constant stirring during the painting operation. To overcome this limitation, painters are required to regularly stir the paint by hand. This stirring is accomplished by physically shaking the pot and gun system and is difficult to standardize. Painters usually stir the material with an amplitude and frequency that varies significantly with the training, experience and preference of the painter. Lack of a regulated stirring method results in significant variation in the performance of the final system.
Moreover, existing suction or gravity-fed systems contain no pressure regulation gauge. These systems use pressurized air flowing across an orifice in the pot to draw the paint out of the pot such that it is propelled by the pressurized air and then released through the nozzle. Since there is no pressure regulation gauge on this system it is impossible to standardize a delivery pressure. Delivery pressure is a critical application parameter in the application of RAM, and variations in application result in performance fluctuations of the final system. With current systems, painters adjust the feed line pressure that again varies based on their experience level. This lack of standardization of pressure settings again results in significant variation in the performance of the final system.
The large volume detached pots overcome the primary disadvantages of the suction or gravity fed systems by using pressurized air to force paint out of the pot into the gun and nozzle (which is regulated by a pressure gauge). Large volume systems also have internal agitation mechanisms. However, their use in application of experimental RAM is limited because of the large volumes required to operate them. The smallest existing systems require one to two quarts of paint to hold a minimum pressure charge and because of inefficient shaping of the pot and the use of lengthy hoses between the pots and the spray guns. As a result the actual volume of paint that can be sprayed is significantly less than the original volume. Although these systems can be utilized to standardize spray applications, their large volume requirements make them unfeasible for many developmental activities. Thus, an improved RAM application system would be desirable.